Muramyl peptides: immunomodulators, sleep factors, and vitamins

Enhancement of immunoglobulin G responses in mice against hepatitis B virus surface antigen, influenza virus hemagglutinin vaccine, and tetanus toxoid by 6-O-acylated muramyl dipeptides

The adjuvant activity of chemically synthesized 6-O-acylated muramyl dipeptides (MDP) was tested in aqueous form. The activity was assessed by determining immunoglobulin G (IgG) titers in sera of mice immunized with hepatitis B virus surface antigen, influenza virus hemagglutinin (HA) vaccine, or tetanus toxoid with an enzyme-linked immunosorbent assay. Administration of 6-O-acyl-MDP analogs with antigens induced marked enhancement of primary and secondary IgG antibody responses and maintained high antibody levels for at least 7 weeks. Among the analogs tested, an MDP methyl ester carrying a 6-O-3-hexadecanoyl-oxytetradecanoyl group (compound 309) exhibited the most intensive adjuvant activity. Its activity was stronger than that of 6-O-2-tetradecylhexadecanoyl (B3O)-MDP used as a positive control. However, accumulation of peritoneal cells and activation of peritoneal macrophages by compound 309 was weaker than that by 6-O-B30-MDP, suggesting that 309 as an immunoadjuvant is more suitable for vaccination in terms of its stronger enhancement of antibody formation and lower induction of inflammatory response than 6-O-B30-MDP.

Dependence of proliferation of Bacteroides forsythus on exogenous N-acetylmuramic acid

Bacteroides forsythus is the first wild-type or mutant bacterium found to require exogenous N-acetylmuramic acid for proliferation and maintenance of cell shape. This implies so far unknown pathways for peptidoglycan synthesis and a strict dependence of B. forsythus on other bacteria in its oral habitat. Addition of N-acetylmuramic acid to conventional bacteriological media allows routine cultivation of this fastidious organism.

Bronchoalveolar lavage T-cell and Ia antigen quantitation by flow cytometry in acute and chronic experimental hypersensitivity pneumonitis

Increasing evidence implicates effector T-cells in the pathogenesis of hypersensitivity pneumonitis. We utilized T-cell- and Ia-specific antibodies, flow cytometry, and computer analysis to quantitate T-cell numbers and Ia expression on lung cells of established rabbit models of acute and chronic hypersensitivity pneumonitis (HSP). We used analysis of variance (ANOVA) and Turkey's follow-up to evaluate group differences. In the acute HSP group, increased percentages of T-cells and greater Ia expression were present on bronchoalveolar lavage (BAL) cells at 24 h after inhalational allergen challenge. Increased BAL T-cell numbers were found in the chronic HSP group produced by repeated inhalation of antigen and muramyl dipeptide, compared to "desensitized" animals and control groups. Both chronic HSP and desensitized groups demonstrated increased Ia expression on BAL cells. Pathology scores for individual animals in both acute and chronic protocols correlated significantly (Pearson correlation coefficients) with total numbers of BAL cells, percentages of T-cells, and percentages of Ia-positive cells recovered. Findings are consistent with the hypothesis that cell-mediated hypersensitivity is a central mechanism in the pathogenesis of experimental hypersensitivity pneumonitis.

Primary structure of the peptidoglycan-derived tracheal cytotoxin of Bordetella pertussis

The etiological agent of whooping cough, Bordetella pertussis, destroys the ciliated epithelial cells lining the large airways of infected individuals. This cytopathology can be reproduced in respiratory epithelium by tracheal cytotoxin (TCT), a small peptidoglycan-related molecule purified from the culture supernatant of growing B. pertussis organisms. Using fast atom bombardment mass spectrometry, we analyzed the positive- and negative-ion spectra of the purified, biologically active material and assigned a mass of 921 daltons to TCT. Analysis of fragment ions in these spectra as well as the spectra of the methyl ester and acetylated derivatives of TCT unambiguously defined the primary structure of TCT as N-acetylglucosaminyl-1,6-anhydro-N-acetylmuramylalanyl-gamma- glutamyldiaminopimelylalanine. TCT is therefore identical with the ciliostatic anhydropeptidoglycan monomer released by Neisseria gonorrhoeae and with the neurologically active slow-wave sleep-promoting factor FSu. These and other structurally related glycopeptides containing muramic acid thus form a family of molecules with remarkably diverse biological activities.

Lipopolysaccharide, muramyl dipeptide and polyinosinic: polycytidylic acid induce the accumulation of inositol phosphates in blood monocytes and lymphocytes

Rabbit macrophages (Mø) and lymphocytes (Ly) incubated with three structurally dissimilar immunomodulators, lipopolysaccharide (bacterial endotoxin, LPS), polyinosinic: polycytidylic acid (poly-I:C) and muramyl dipeptide (MDP), were found to accumulate inositol phosphates (IPs) in a concentration- and time-dependent manner. The threshold concentration of LPS necessary for an increase in IPs in both cell types was less than 1 ng/ml and a maximum effect was observed between 1 and 10 micrograms/ml. The threshold concentrations for poly-I:C and MDP were between 0.1 and 1 microgram/ml for both cell types. Significant increases in the concentration of inositol phosphates occurred between 30 and 60 min after challenge of either cell type with any of the three agents studied. In addition, all three immunomodulators produced a greater accumulation of IPs in macrophages than in mixed lymphocytes and after 2 h appeared to approach a maximum in macrophages, whereas the IPs level in lymphocytes appeared to be still rising after 2 h. In Mø and Ly the IPs level was increased within 10 min of incubation in the presence of either PGE2 or medium previously obtained from cells incubated with LPS. In addition, anisomycin (a protein synthesis inhibitor) and ketoprofen (a cyclo-oxygenase inhibitor) inhibited the LPS-stimulated increase of IPs accumulation in both cell types. These two observations suggest that the LPS-stimulated increase in IPs in macrophages and lymphocytes is mediated by a protein intermediate and possibly a prostanoid.

Photoaffinity labelling of macrophages and B-lymphocytes using 125I-labelled aryl-azide derivatives of muramyldipeptide

Two 125I-labelled aryl-azide derivatives of MDP have been synthesized. Photoaffinity labelling experiments demonstrated cell surface binding sites for muramylpeptides on activated B-lymphocytes and intracellular muramylpeptides binding protein(s) of 40-45 kD in rat alveolar macrophages.

Immunostimulatory activity of 1-O-acylated muramyl dipeptides, with or without a 6-O-phosphoryl group, in aqueous form

Immunostimulatory effects of 1-O-acylated derivatives of N-acetyl-muramyl-L-alanyl-D-isoglutamine (MDP) methyl ester, with or without the 6-O-phosphoryl group, on augmentation of IgG antibody response against influenza hemagglutinin (HA) vaccine, in vivo macrophage activation and enhancement of non-specific host resistance against Pseudomonas aeruginosa infection were investigated. The activities were tested intraperitoneally (i.p.) in mice administered test samples solubilized or suspended in saline. The introduction of longer chain acyl groups into MDP methyl esters significantly induced enhancement of the IgG antibody response. Among them, the adjuvant activity of 1-O-linked 2-tetradecylhexadecanoyl (B30)-MDP methyl ester was comparable to that of 6-O-B30-MDP used as a positive control. Phosphorylation at the C6 position of the acylated MDP analogs did not induce a significant increment in the activity. With respect to phagocytic, cellular acid phosphatase and cytostasis-inducing activities, i.p. administration of acylated MDP analogs caused significant increment and activation of peritoneal macrophages. The cytostasis-inducing activity of 1-O-octadecanoyl- or 1-O-B30-MDP methyl ester with or without a phosphoryl group was more intensive than that of 6-O-B30-MDP. Acylated MDP analogs enhanced non-specific resistance against P. aeruginosa infection when the analogs were administered i.p. on the day before the infection. The enhancement was closely related to the accumulation of polymorphonuclear cells in the peritoneal cavity. The manifestation of these immunostimulatory activities by 1-O-acylated MDP analogs depended closely on the increasing carbon chain length of fatty acid substituents when administered in aqueous form.

Modulation of interferon-gamma-induced major histocompatibility (MHC) and CD14 antigen changes by lipophilic muramyltripeptide MTP-PE in human monocytes

The lipophilic muramylpeptide derivative muramyltripeptide-phosphatidylethanolamine (MTP-PE, 0.05 to 5 micrograms/ml) and human recombinant interferon-gamma (rIFN-gamma, 1 to 100 U/ml) were applied singly or in combination to fresh human mononuclear blood leucocytes in vitro. After 15 to 72 hr incubation, culture- and drug-induced changes in beta 2-microglobulin (MHC class I associated), HLA-DR (MHC class II), and Leu-M3 (CD14) antigen expression were investigated by flow cytometry; changes in monocyte morphology (forward light scatter and side scatter) were assessed by scatter analysis. It was found that (1) rIFN-gamma caused a simultaneous down-regulation of the CD14 antigen and an up-regulation of MHC class I and class II molecules on the surface of cultured monocytes; (2) MTP-PE, which by itself failed to influence the expression of these antigens, synergized with rIFN-gamma in increasing MHC antigens and reducing CD14; (3) at high concentrations rIFN-gamma reduced monocyte viability to a small but significant extent and this effect was further potentiated by MTP-PE; and (4) untreated monocytes in culture showed an apparently MTP-PE-insensitive increase in size, density, and beta 2-microglobulin, HLA-DR, and CD14 antigen expression. The influence of MTP-PE on rIFN-gamma-induced surface marker changes may contribute to its immunoadjuvant activity in vivo.

Interferon-gamma and tumor necrosis factor induce the L-arginine-dependent cytotoxic effector mechanism in murine macrophages

We tested several monokines and muramyl dipeptide (MDP) to determine whether they induce the L-arginine-dependent effector mechanism in cultured murine macrophages. Recombinant interferon-gamma (rIFN-gamma) and recombinant tumor necrosis factor (rTNF) synergize to induce nitrite (NO2-) and nitrate (NO3-) synthesis from L-arginine as well as to cause inhibition of the iron-dependent enzyme aconitase in macrophages. Unlike rTNF, recombinant interleukin 1 (rIL 1) and rIL 6/B cell stimulatory factor 2 (rIL 6/BSF-2) did not act as cofactors when added to macrophages in the presence of rIFN-gamma. rIFN-gamma plus MDP induced the L-arginine-dependent effector mechanism in murine macrophages. However, induction by rIFN-gamma plus MDP was inhibited by anti-rTNF antibodies which suppressed both NO2-/NO3- synthesis and aconitase inhibition. This result indicates that endogenously produced TNF is involved in the induction of the L-arginine-dependent effector mechanism when MDP is the co-stimulant with rIFN-gamma. In contrast, anti-rTNF antibodies did not fully suppress the effect of combining rIFN-gamma and lipopolysaccharide, suggesting that, in this case, activation of the L-arginine-dependent effector pathway may involve more than induction of TNF synthesis by the macrophages. These results provide information, at a biochemical level, on a mechanism through which combination of IFN-gamma and TNF can modulate macrophage functions involved in the control of cell proliferation.

Immunological activities of multiprenylacetyl derivatives of muramyldipeptides

The immunological properties of six kinds of multiprenylacetic acids and six kinds of multiprenylacetyl muramyldipeptide (MDP) derivatives were examined by using experimental models in mice and guinea-pigs. All the multiprenylacetyl MDP derivatives, particularly TMD-232, showed potent adjuvant activity on the circulating antibody formation against bacterial alpha-amylase in mice, and induction of delayed-type hypersensitivity to monoazobenzenearsonate N-acetyl-L-tyrosine in guinea-pigs. All multiprenylacetic acid preparations tested in this study, however, showed no adjuvant activity in these immune systems. Both TMD-17 and TMD-232 entrapped into multilamellar vesicles showed potent host stimulation activity against Sendai virus infection in mice.

Alteration of sleep in rabbits by Staphylococcus aureus infection

Abundant evidence suggests that sleep might be altered during infectious disease, although the relationship between sleep and infectious disease has never been examined systematically. To address this issue, we determined the effects of Staphylococcus aureus infection on rabbit sleep. Rabbits inoculated intravenously with S. aureus demonstrated the expected physiological changes consistent with a state of infectious disease (e.g., lymphopenia, neutrophilia, and fever), as well as time-dependent changes in sleep patterns. The sleep changes were characterized initially by increases in (i) the time spent in slow-wave sleep, (ii) the electroencephalographic slow-wave amplitudes during slow-wave sleep, and (iii) the duration of individual bouts of slow-wave sleep. At 20 to 36 h after inoculation, sleep responses fell to levels below corresponding control values for 6 to 12 h. At 6 to 10 h after inoculation, rapid-eye-movement sleep was suppressed and remained at low levels throughout the remainder of the 48-h recording period. These effects of bacterial infection on sleep were attenuated by antibiotic (cephalothin) therapy. Inoculation with killed bacteria produced similar changes in sleep and other physiological parameters, although significantly higher numbers of organisms were required to produce equivalent responses. We postulate that changes in sleep may represent an adaptive response of the host to infectious disease.

Comparative susceptibility of a peptidoglycan monomer from Brevibacterium divaricatum and its anhydromuramyl analogue to hydrolysis with N-acetylmuramyl-L-alanine amidase. Isolation and characterization of anhydromuramyl-peptidoglycan monomer

Peptidoglycan monomer, GlcNAc-beta-(1----4)-MurNAc-L-Ala-D-iGln[ (L)-meso-A2pm-(D)-amide-(L)-D-Ala-D-Ala] (PGM), from Brevibacterium divaricatum is composed of the disaccharide pentapeptide containing muramic acid with a reducing end (ca. 90-95%) and of the anhydromuramyl analogue (anhydromuranyl-PGM; ca. 5-10%), according to analysis by high-performance liquid chromatography (HPLC) and fast atom bombardment mass spectrometry (FAB-MS). The two peptidoglycan analogues cannot be separated by simple physico-chemical procedures. The enzyme N-acetylmuramyl-L-alanine amidase (mucopeptide amidohydrolase, E.C. 3.5.1.28) cleaves the bond between N-acetylmuramic acid and L-alanine in the PGM molecule. It is shown that anhydromuramyl-PGM is also a substrate for the amidase. In a preparation containing both analogues, the amidase hydrolyses preferentially PGM rather than anhydromuramyl-PGM. The experimental conditions for treatment with the amidase were adjusted with respect to time and enzyme concentration to allow hydrolysis to proceed for several hours. The course of hydrolysis was followed by analysis of the unhydrolyzed substrate by HPLC, and FAB-MS at predetermined time intervals; after 6 h, the amount of anhydromuramyl-PGM in the unhydrolyzed substrate increased to 25% as compared to the starting material containing only 6%. Such a mixture was suitable for separation of components by preparative thin-layer chromatography and for isolation of completely purified PGM and the corresponding anhydromuramyl analogue containing an intramolecular 1,6-anhydromuramyl end. The separated purified compounds were characterized by HPLC and their structure confirmed by FAB-MS-MS.

N-acetylmuramyl-L-alanyl-D-isoglutamine stimulates the immune response of B cells. Use of fast protein liquid chromatography to purify a novel monokine involved in this effect

The immune response of murine B cells, which requires the presence of various cytokines, was stimulated by N-acetylmuramyl-L-alanyl-D-isoglutamine. A novel monokine involved in this effect has been partially purified from the conditioned medium of peritoneal macrophages by using affinity chromatography on Blue-Sepharose and high-performance liquid chromatography. Hydrophobic interaction chromatography was highly efficient in removing almost all protein contaminants. The resulting biologically active material exhibited heterogeneity in ion-exchange chromatography, and apparent isoelectric points between 5.2 and 5.5 on chromatofocusing. Its apparent molecular weight, as determined by size-exclusion filtration, was about 35,000. Preliminary results on the kinetics of appearance of intracellular biological activity suggested that the monokine could also be obtained from cytoplasmic extracts.

The synthetic immunomodulator muramyl dipeptide (MDP) can stimulate activated B cells

The synthetic immunomodulator muramyl dipeptide (MDP) has previously been shown to be able to synergize with lymphokines in enhancing the specific immune response of purified splenic B cells. Here, we have examined the effect of MDP in the process of B cell activation. We found that MDP alone was ineffective on the proliferation of either murine resting or in vivo activated B cells, whereas it enhanced the DNA synthesis of B cells once stimulated with anti-IgM antibodies. In agreement with these findings, cell cycle analysis by flow cytometry after acridine orange staining indicated that MDP by itself could not trigger the entry into the G1 phase of the cell cycle of nonactivated B lymphocytes. In contrast, in the presence of anti-IgM antibodies plus BSF-1, MDP promoted further cell cycle progression preferentially into the G1B compartment and also through the G2/M phase. A kinetic study showed that MDP was the most effective when added after the activation of B cells by anti-IgM antibodies plus BSF-1. Our present results suggest that functional receptors for MDP may be expressed on already cycling B cells.

DSIP--a tool for investigating the sleep onset mechanism: a review

Delta-Sleep-Inducing Peptide (DSIP) has several physiological effects in addition to its ability to promote sleep in animals under certain conditions. These effects include modification in thermoregulation, heart rate, blood pressure, pain threshold, and in the lymphokine system. DSIP effects are circadian cycle-dependent. Moreover, some of DSIP effects appear before neurological or behavioral signs of sleep. DSIP may promote peripheral preparatory physiological mechanisms associated with sleep onset.

Enhancement of B-cell stimulation by muramyl dipeptide through a mechanism not involving interleukin 1 or increased Ca2+ mobilization or protein kinase C activation

Muramyl dipeptide (MDP) enhanced mitogenic stimulation of mouse lymphocytes by polyclonal B cell activators (peptidoglycan, lipopolysaccharide, Staphylococcus aureus Cowan I cells, and pokeweed mitogen), but not by T-cell mitogens (phytohemagglutinin and concanavalin A). Only adjuvant-active MDP analogs were effective, whereas adjuvant-inactive MDP analogs, muramic acid, peptidoglycan pentapeptide, and low Mr digests of peptidoglycan were not. The half-maximal enhancement was seen at 5-10 microM MDP and occurred at both optimal and suboptimal concentrations of B cell mitogens. The enhancing effect of MDP was exerted on the B cells, since it was T cell- and macrophage-independent and was not mediated by IL-1. MDP was effective during the first 12 hrs of culture, and most strongly enhanced the mitogen-induced DNA synthesis, although significant enhancement of RNA synthesis and B cell differentiation into antibody-secreting cells was also observed. The enhancement of mitogenic response was not due to changed requirements for extracellular or intracellular Ca2+ or to increased activation of protein kinase C. These results demonstrate a novel immunoenhancing effect of MDP that should be useful in the studies on the mechanism of B cell activation.

Chapter 12 Compound Biopolymers and Biooligomers

This chapter is devoted to the separation of simple saccharides. In this chapter, the rapid chromatographic separation of natural oligomeric or polymeric compounds containing important molecular moieties of a different type are discussed, such as nucleoprotein complexes, glycolipids, glycopeptides and glycoside oligomeric derivatives. In addition, separations of several natural complex substances that are not well known are discussed. This chapter concludes with a brief discussion on the separation techniques used for the miscellaneous polymeric and oligomeric substances.

Suppression of Sendai virus growth by treatment with N alpha-acetylmuramyl-L-alanyl-D-isoglutaminyl-N epsilon-stearoyl-L-lysine in mice

Mice that received N alpha-acetylmuramyl-L-alanyl-D-isoglutaminyl-N epsilon-stearoyl-L-lysine [MDP-Lys (L18)] were resistant to Sendai virus infection. In these protected mice, a significant growth inhibition of the virus was confirmed repeatedly at 10(0.2) to 10(0.4) of haemadsorbing units at an early non-specific phase but not at a late virus-eliminating phase of the infection. Virus growth was enhanced by treatment with silica but not by treatment with anti-asialo GM1 serum in MDP-Lys (L18)-treated mice. Peritoneal adherent cells activated by MDP-Lys(L18) showed an enhanced uptake and ability to inactivate Sendai virus in vitro. Excess interferon production in MDP-Lys (L18)-treated mice was seen on day 1 but not on days 2 to 7 of the infection. The possible role of macrophages and interferon in providing non-specific protection against Sendai virus in the MDP-Lys (L18)-treated mice is discussed.

Stimulation of non-specific host resistance against Sendai virus and Escherichia coli infections by chitin derivatives in mice

The efficacy of chitin derivatives on non-specific host resistance to Sendai virus and Escherichia coli infections was studied in mice. Seventy percent deacetylated chitin (DAC-70) and N-trimethylated DAC-70 [DAC-70(Me)3] showed protective activity against Sendai virus infection; however, carboxymethyl-chitin (CM-chitin) did not. DAC-70 also showed protective activity against E. coli infection.

A novel muramyl peptide derivative stimulates tumoricidal activity of macrophages and antibody production by B cells

A novel analog of MDP, the 3'-iodo-4'-azido-L-phenylalanine methyl ester derivative of N-acetyl-L-alanyl-D-isoglutamine, has been prepared. This compound is capable of activating macrophages to the tumoricidal state and increasing the specific immune response of B cells. It thus appears to exhibit similar biological activities to MDP. Moreover, this compound is of potential interest for receptor photolabelling studies.

Use of mannosylated liposomes for in vivo targeting of a macrophage activator and control of artificial pulmonary metastases

From a mannosylated mycobacterial phospholipid, we prepared an original type of liposome which was taken up by macrophages by means of the mannose/fucose receptor. When a lipophilic immunomodulator, MDP-L-alanyl-cholesterol (MTP-CHOL) was included in such liposomes, they were able to activate WAG rat alveolar macrophages for cytotoxicity against syngeneic tumour cells in vitro. The presence of suboptimal levels of endotoxin was essential for this activation. Cytotoxic macrophages could also be induced in vivo by injecting immunomodulator-loaded liposomes intravenously 24 h before harvesting macrophages. A decrease in experimental pulmonary colonies arising from i.v. injected tumour cells was observed following repeated administration of such liposomes.

Structural requirements of muramylpeptides for induction of necrosis at sites primed with Mycobacterium tuberculosis in guinea pigs

Intracutaneous injection of N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) in guinea pigs caused an extensive necrotic reaction in footpads prepared by injection of heat-killed Mycobacterium tuberculosis in water-in-mineral-oil emulsion. We examined a variety of analogs and derivatives of muramylpeptides for their ability to provoke this reaction. A maximum and a minimum structure responsible for the necrotic reaction were found to be N-acetylglycosaminyl-beta(1-4)-N-acetylmuramyl-tripeptide (GlcNAc-MurNAc-L-Ala-D-isoGln-meso-A2pm) and MDP, respectively. An unexpected finding was that GlcNAc-MurNAc-tetrapeptides having L-amino acids at their C termini, unlike comparable compounds having C-terminal D-amino acids, exhibited definite necrosis-inducing activity, probably due to their tendency to undergo in vivo degradation to GlcNAc-MurNAc-tripeptide. Introduction of some acyl groups, especially the stearoyl group, to the 6-O position of the muramic acid or the peptide moiety of muramylpeptides increased the necrosis-inducing activity of the parent molecules. However, this was not observed with 1-thio-muramic acid analogs of MDP. Modification of the alpha- or gamma-carboxyl groups of the glutamic acid residues of muramylpeptides tended to decrease their necrosis-inducing ability. Analogs and derivatives of muramylpeptides which are capable of inducing necrosis at a primed site, with few exceptions, exhibited powerful adjuvanticity against ovalbumin in guinea pigs. However, the reverse was not necessarily true.

A comparative 1H-n.m.r. study of MurNAc-L-Ala-D-iGln (MDP) and its analogue murabutide: evidence for a structure involving two successive beta-turns in MDP

The active principle, MurNAc-L-Ala-D-iGln (MDP), of complete Freund's adjuvant and its analogue, MurNAc-L-Ala-D-Gln-OnBu (murabutide), which express immunomodulatory as well as other biological properties, have been studied by 2D-1H-n.m.r. spectroscopy at 500 MHz. The results suggest the presence in MDP of two successive turns involving the MurNAc-L-Ala and L-Ala-D-iGln moieties, respectively, whereas only the former turn persists in murabutide. This turn mimics the type II beta-turn found in L-D depsipeptides, whereas the other is a typical type II beta-turn for L-D peptides.

Bacterial peptidoglycans as modulators of sleep. I. Anhydro forms of muramyl peptides enhance somnogenic potency

Chemically defined muramyl peptides (MPs), derived primarily from enzymatic digests of Neisseria gonorrhoeae peptidoglycan, were used to define the structural determinants of MP-mediated somnogenic activity. One of these, i.e. N-acetylglucosaminyl-N-acetyl-1,6-anhydro-N-acetylmuramyl-alanyl-glutamy l- diaminopimelyl-alanine, was structurally identical to the major naturally occurring MP previously detected in mammalian brain and urine. The somnogenic potency of this MP was similar to that of the corresponding disaccharide pentapeptide containing an additional alanine at the C-terminus and the analogous anhydro-muramic acid-containing monosaccharide tetrapeptide lacking the glucosamine moiety. Infusion of as little as 1 pmol of these highly active MPs increased significantly the percentage of slow-wave sleep in experimental animals. In fact, each of 5 anhydro-muramyl disaccharide peptides tested was somnogenic at a dose of 10 pmol or less and, as far as tested, the activity was affected only slightly by the length or composition of the peptide side chain. However, none of a matched set of analogous MPs, differing only in replacement of the anhydro-muramyl end by a hydrated muramic acid residue, was somnogenic at this dose. A modified form of the hydrated muramyl tripeptide containing a free amide on the diaminopimelic acid residue was completely inactive in amounts up to 1000 pmol. Together, the current data suggested: that the anhydro-muramic acid end (but not the glucosamine moiety) is essential for maximal somnogenic potency; and that amidation of carboxyl groups on the peptide-side chain may block MP-mediated somnogenic activity.

Analgesic effects of N-acetylmuramyl-L-alanyl-D-isoglutamine in decreasing the acetic acid-induced abdominal-writhing response

A new pharmacological action of N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) is described. Pretreatment of male ddY mice with MDP, but not its biologically inactive analogs, significantly decreased the frequency of acetic acid-induced writhing movements more effectively than did acetylsalicylic acid (aspirin). The analgesic effect of MDP, however, was less than that of a narcotic antagonist, pentazocine.

Enhancement of endotoxin lethality and generation of anaphylactoid reactions by lipopolysaccharides in muramyl-dipeptide-treated mice

Intravenous injection of muramyl dipeptide (MDP) and Salmonella lipopolysaccharides (LPS) enhanced lethal toxicity of the LPS in C57BL/6 mice. This was true for S (smooth)- and R (rough)-form LPS and free lipid A. Enhancement of toxicity was maximum when the LPS was administered 4 h after MDP, at which time the lethal doses for 50% of mice of S- and R-form LPS and free lipid A were between 1 and 10 micrograms, compared with more than 100 micrograms in normal animals. This sensitization was absent in endotoxin-resistant C3H/HeJ mice. Lethality usually commenced 15 h after LPS injection and was complete after 72 h. Higher doses of some S-form LPS (100 micrograms or more) administered 4 h after MDP led to a strong anaphylactoid reaction within 10 to 20 min of injection, with lethal outcomes in less than 1 h after LPS administration. This early anaphylactoid reaction was observed for various mouse strains, including LPS-resistant C3H/HeJ mice, but it was very weak or completely absent with R-form LPS or free lipid A even in concentrations of up to 1,000 micrograms. A strong anaphylactoid reaction comparable to that seen with S-form LPS was also obtained, after MDP treatment, with an LPS of low toxicity prepared from Bacteroides gingivalis. It is noteworthy that oral administration of MDP also contributed to the anaphylactoid reaction and enhanced the late-phase lethality of LPS. The present findings strongly suggest that the early- and late-phase reactions induced by MDP and LPS are caused by different mechanisms.

Muramyl dipeptide, amphetamine, and physostigmine: effects on sleep of rabbits

Muramyl peptides (MPs) are constituents of bacterial cell walls and mammalian tissue. Some MPs have the capacity to enhance slow-wave sleep (SWS). In rabbits, it was unknown whether MPs enhanced SWS by prolonging SWS episodes or by increasing the number of SWS episodes. In rabbits, there is a frequent alternation between sleep and waking; thus, demonstration of induction of new SWS episodes is difficult unless pharmacologic manipulations are used. We injected amphetamine subcutaneously to reduce duration of sleep (from about 45% to 20%) for a period of two hours; it reduced the number of SWS episodes. Muramyl dipeptide (MDP: NAM-L-ala-D-isogln) injected into a lateral ventricle one hour before amphetamine significantly increased the number of SWS episodes. Physostigmine, a cholinergic agonist, was also used. By itself, physostigmine greatly reduced SWS and rapid eye movement sleep. Pretreatment of animals with MDP two hours before physostigmine injection failed to reverse subsequent physostigmine-induced wakefulness. We conclude that MDP has the ability to induce SWS episodes but does not act directly on the thalamocortical cholinergic mechanisms of EEG phenomena. Our results, together with earlier evidence on anatomical levels of action of amphetamine and physostigmine, suggest that the somnogenic mechanisms of MPs likely involve the midbrain.

The effects of immunomodulating peptidoglycan monomer and muramyl dipeptide on hepatic microsomal UDP-glucuronyltransferase and beta-glucuronidase

The effects of immunomodulating peptidoglycans, peptidoglycan monomer (PGM) and muramyl dipeptide (MDP), on hepatic microsomal UDP-glucuronyltransferase (uridine diphosphoglucuronate glucuronosyl transferase, EC 2.4.1.17) and beta-glucuronidase (beta-D-glucuronide glucuronohydrolase, EC 3.2.1.31) were tested in female C57Bl mice. 4-Methylumbelliferone and p-nitrophenol were used as representative substrates for one functional form of UDP-glucuronyltransferase (GT1) and testosterone for the second functional form (GT2) of the enzyme. Both PGM and MDP were found to transiently inhibit the activity of UDP-glucuronyltransferase. There was no significant difference in the magnitude of inhibition of the two functionally different enzyme forms. The activity of microsomal beta-glucuronidase was tested using 4-methylumbelliferyl glucuronide and p-nitrophenyl glucuronide as substrates. Time dependent transient inhibition of beta-glucuronidase activity was observed with both peptidoglycans. In addition, the effect of MDP on cytochrome P-450 was tested, since we have shown previously that PGM affected this system. MDP decreased the content of cytochrome P-450 and inhibited the activity of related enzymes.

Relationship of metabolism and immunostimulating activity of peptidoglycan monomer in mice after three different routes of administration

[14C] Peptidoglycan monomer, GlcNAc-MurNAc-L-Ala-D-isoglutamine-meso-diaminopimelic acid (omega NH2)-D-Ala-D-Ala (PGM) was administered to mice by the intravenous (i.v.), subcutaneous (s.c.) or peroral (p.o.) routes. The data on distribution of radioactivity and excretion of radioactive products, as well as the data on immunostimulating effects are presented on the comparative basis for PGM administered by three different routes. When injected i.v. or s.c., the major part of applied radioactivity was found excreted in urine, partly as unchanged original compound and partly as the corresponding pentapeptide, L-Ala-D-isoglutamine-meso-diaminopimelic acid (omega NH2)-D-Ala-D-Ala. If administered p.o., the major part of the radioactivity was retained in the stomach and intestinal tract for several hours. The drop in radioactivity in these organs was followed by exhalation of 14CO2 thus indicating extensive degradation of the original molecule. PGM stimulates the humoral immune response to sheep red blood cells in mice if administered i.v. or s.c., but is completely inactive if administered p.o.. Thus, absence of immunostimulating activity following p.o. administration might be explained by extensive metabolic degradation of peptidoglycan monomer.

The lipophilic muramyltripeptide MTP-PE, a biological response modifier, is an activator of protein kinase C

The lipophilic immunomodulator MTP-PE is able to activate purified protein kinase C (PKC) by substituting phosphatidyl-serine (PS) or the synthetic diacylglycerol, DiC8, in the assay system. In addition, MTP-PE inhibited [3H]-phorbol-12, 13-dibutyrate ([3H]-PDBu) binding to PKC in a reconstituted receptor system as well as on intact cells (MCF-7). Furthermore, MTP-PE was also able to reduced the epidermal growth factor binding of MCF-7 cells to an extent similar to that found with DiC8 or PDBu. These data indicate that MTP-PE is able to compete for the phorbol ester binding site on PKC both in vivo and in vitro. The components of the MTP-PE molecule, MTP (muramyl-tripeptide) and PE (phosphatidylethanolamine) exerted only marginal effects on PKC activity, did not affect the phorbol ester binding of PKC and the EGF binding of intact MCF-7 cells. Our results suggest that only the complete molecule of the immunomodulator MTP-PE is able to interact with PKC.

Adjuvant activity of 6-O-acyl-muramyldipeptides to enhance primary cellular and humoral immune responses in guinea pigs: adaptability to various vehicles and pyrogenicity

Thirteen 6-O-acyl-N-acetylmuramyl-L-alanyl-D-isoglutamines (6-O-acyl-MDPs), including four inactive D-isoasparagine and L-isoglutamine analogs, were tested for their pyrogenicity and immunopotentiating activity to stimulate primary humoral and cellular immune responses in guinea pigs to a model protein antigen, ovalbumin, when administered in various vehicles. Among them, derivatives whose muramic acid residue was substituted by alpha-branched (and beta-hydroxylated) higher fatty acids at the carbon-6 position, especially 6-O-(2-tetradecylhexadecanoyl)-MDP (B3O-MDP) and, to a lesser extent, 6-O-(3-hydroxy-2-docosylhexacosanoyl)-MDP (BH48-MDP) and its L-serine analog [BH48-MDP(L-Ser)], were found to exert strong adjuvant activity in both the induction of delayed-type hypersensitivity and the stimulation of circulating precipitating antibody levels when combined with nonirritating vehicles (liposomes, squalene-in-water emulsion, and phosphate-buffered saline). These vehicles did not efficiently support the adjuvant activity of MDP, the parent molecule of the above lipophilic derivatives. Pyrogenicity tests showed that introduction of alpha-branched higher fatty acid groups but not of straight, long-chain fatty acids at the 6-position of the muramic acid residue resulted in marked decrease of the pyrogenicity inherent to MDP via intravenous administration.

Muramyl dipeptide induces acute joint inflammation in the mouse

Acute joint inflammation was produced in BALB/c mice by a single intravenous injection of synthetic muramyl dipeptide (MDP), its stereoisomers and 6-O-acyl derivatives of MDP. Four adjuvant-active, but not five adjuvant-inactive MDP analogs induced acute swelling and erythema of the ankles and wrists which were detected around 6-10 hr, reached the maximum severity by 18-24 hr and subsided by days 3 to 4 after injection. Introduction of the stearoyl group, but not the alpha-branched long chain fatty acid group into the C-9 hydroxyl group of MDP enhanced and prolonged the joint lesions compared with MDP.

Curative properties of muramyl dipeptide in experimental Naegleria meningoencephalitis

Naegleria fowleri is a free-living amoeba which causes a fatal meningoencephalitis in man. Mice injected with the immunostimulant MDP or an attenuated 11RX strain of Salmonella enteritidis showed some resistance to an intranasal challenge with N. fowleri. In addition it was observed that some of the mice infected with N. fowleri and showing symptoms of naegleria meningoencephalitis, given a single injection of MDP were cured of this disease. Our findings suggest that the use of immunostimulants could be a new approach in the quest for therapeutic agents for this disease.

Effect of muramyl dipeptide and its stearoyl derivatives on resistance to Sendai virus infection in mice

The efficacy of N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP), 6-O-stearoyl-MDP (L18-MDP), N alpha-acetylmuramyl-L-alanyl-D-isoglutaminyl-N epsilon-stearoyl-L-lysine (MDP-Lys-L18) and N-stearoylmuramyl-L-alanyl-D-isoglutamine (2N-L18-MDP) for augmenting host-resistance to viral infection was examined in Sendai virus infected mice. L18-MDP and MDP-Lys-L18 augmented the non-specific host-resistance to infection with Sendai virus. MDP showed a slight enhancement of host-resistance to this infection but 2N-L18-MDP was ineffective. The protective effect of MDP-Lys-L18 was seen only when the drug was administered a few days before the virus challenge. The intranasal administration of MDP-Lys-L18 was effective at 1 microgram but only slight activity was observed in mice treated intravenously or intraperitoneally even at the 100 microgram dose level. MDP-Lys-L18 treatment preceding infection augmented interferon production in the lung of the mice but MDP-Lys-L18 treatment alone induced no interferon.

The involvement of brain structures in the adjuvant effect of muramyl dipeptide

With the aid of small electrolytic lesions we have studied the possible participation of brainstem structures in the adjuvant activity of muramyl dipeptide (MDP). The results suggest the involvement of the serotonergic groups B6.7.8 and serotonergic pathways in the upper region of the reticular formation. Since lesions in the caudal parts of reticular formation in the area of aminergic groups A1.3.5.7 with the participation of corresponding pathways also influenced the adjuvant effect of MDP the possible role of noradrenaline is also implicated.

Muramyl peptides and serotonin interact at specific binding sites on macrophages and enhance superoxide release

Serotonin at low micromolar concentrations inhibited binding of two [125I]-labeled muramyl peptides to resident mouse peritoneal cells and to a macrophage-derived cell line, PU5-1.8-F7. Binding of [3H]serotonin was inhibited in parallel fashion. Overnight incubation with serotonin or muramyl peptide enhanced the release of superoxide by both types of cells when later stimulated with phorbol myristate acetate. Serotonin antagonists decreased binding of muramyl peptide and serotonin and diminished the subsequent enhancement of superoxide release. A cell line variant lacking detectable binding sites for muramyl peptide was far less responsive (superoxide release) than the parent line, to either drug. The data are consistent with sharing of a common set of receptors on the macrophage by muramyl peptide and serotonin and with involvement of these receptors in enhancing superoxide release.

The ability of thapsigargin and thapsigargicin to activate cells involved in the inflammatory response

The ability of thapsigargin and thapsigargicin to activate mast cells and leukocytes has been investigated. The thapsigargin-induced histamine release from rat peritoneal mast cells was found to be dependent on the concentration of thapsigargin, the purity of the mast cell preparations, and the number of mast cells in suspension. Thapsigargin induced histamine release from human basophil leukocytes. Thapsigargin induced beta-glucuronidase and lysozyme release from human neutrophil leukocytes. Thapsigargin caused a release of histamine from mesentery, lung, and heart mast cells of the rat, but only to a minor extent from the corresponding guinea-pig cells. Thapsigargicin induced histamine release from mesentery, lung, and heart mast cells of the rat at concentrations from 0.1 microM but provoked only a release from the corresponding guinea-pig cells in the concentration-range 0.16 to 1.6 microM. Thapsigargin increased the cytoplasmic free calcium level in intact human blood platelets at concentrations from 3.0 nM.

Combinations of two synthetic adjuvants: synergistic effects of a surfactant and a polyanion on the humoral immune response

Synergistic effects of two synthetic adjuvants, dimethyldioctadecylammonium bromide (DDA) and dextran sulfate (DXS) on the humoral response to sheep red blood cells (SRBC) were investigated. Mice received intraperitoneal (ip) injections of adjuvant and antigen simultaneously. The number of plaque-forming cells (PFC) in the spleen were determined 5 days later and circulating anti-SRBC antibodies were measured till 16 weeks after immunization. Although combinations of DDA and DXS were very effective in enhancing the PFC response to both moderate (2 X 10(7] and low (2 X 10(6] doses of SRBC, synergy between the adjuvants was only observed at the low dose of SRBC. Optimal augmentation of the primary response to the low antigen dose was evoked by the combination of the highest dose tested of either adjuvant (1 mumol DDA and 1 nmol DXS) resulting in a 560-fold increase of the number of PFC in the spleen as compared to controls. Even combinations of relatively small amounts of both adjuvants were very effective in augmenting the response to SRBC. Mice receiving half the amounts of both adjuvants with 2 X 10(6) SRBC displayed increased numbers of PFC in the spleen at Day 5 as well as increased titers of total anti-SRBC antibodies at Week 1 and Week 2 and 2-mercaptoethanol-resistant antibodies from Week 4 till Week 16 as compared to the calculated sum of responses in mice which received either DDA (0.05 mumol per mouse) or DXS (0.05 nmol per mouse). The mechanism behind the synergy between these adjuvants is discussed and the possibility of discerning adjuvants on their modes of action is suggested.

Chemotherapy and the immune response in parasitic infections

There are comparatively few studies concerned specifically with chemotherapy of parasitic infections and its relationship with the immune status of the host being treated. In one sense this is hardly surprising. The disciplines of chemotherapy and immunology have developed independently, and the search for effective drugs has for the most part been an empirical process; when a compound showing some activity has emerged the tendency has been to look for analogues with even greater parasiticidal properties rather than to consider whether effectiveness of the parent compound could be improved if the immune status of the host were different. In many cases, test systems for drug development have actually been selected to reduce as far as possible the complications f an immune response. Thus acute, fatal infections are commonly used for the screens, and questions such as the level of specific resistance at the time of treatment, immunodepression by the parasite, and increased resistance to challenge following chemotherapy are generally irrelevant.